U.S. patent number 8,817,998 [Application Number 12/794,759] was granted by the patent office on 2014-08-26 for active vibratory noise control apparatus.
This patent grant is currently assigned to Honda Motor Co., Ltd.. The grantee listed for this patent is Toshio Inoue. Invention is credited to Toshio Inoue.
United States Patent |
8,817,998 |
Inoue |
August 26, 2014 |
Active vibratory noise control apparatus
Abstract
An active vibratory noise control apparatus includes a basic
signal generator configured to output a basic sine wave signal and
a basic cosine wave signal. An adaptive finite impulse response
filter is configured to output a control signal to cancel the
vibratory noise. A vibratory noise cancelling device is configured
to generate vibratory-noise canceling sound. An error signal
detector is configured to output an error signal. A reference
signal generator is configured to output a reference signal and
corrects the basic cosine wave signal and the basic sine wave
signal based on correction values. A buffer is configured to
accumulate a number of reference signals corresponding to a number
of taps of the adaptive finite impulse response filter. A filter
coefficient updating device is configured to sequentially update
filter coefficients of the adaptive finite impulse response filter
to minimize the error signal.
Inventors: |
Inoue; Toshio (Wako,
JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Inoue; Toshio |
Wako |
N/A |
JP |
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|
Assignee: |
Honda Motor Co., Ltd. (Tokyo,
JP)
|
Family
ID: |
43527016 |
Appl.
No.: |
12/794,759 |
Filed: |
June 6, 2010 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20110026723 A1 |
Feb 3, 2011 |
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Foreign Application Priority Data
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Jul 31, 2009 [JP] |
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2009-179122 |
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Current U.S.
Class: |
381/71.9 |
Current CPC
Class: |
G10K
11/17823 (20180101); G10K 11/17855 (20180101); G10K
11/17883 (20180101); G10K 11/17854 (20180101); G10K
2210/121 (20130101); G10K 2210/1282 (20130101); G10K
2210/511 (20130101); G10K 2210/3028 (20130101) |
Current International
Class: |
G10K
11/16 (20060101); H03B 29/00 (20060101) |
Field of
Search: |
;381/71.4,71.2,71.8-71.12 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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001909262 |
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Apr 2008 |
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EP |
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2004-361721 |
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Dec 2004 |
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JP |
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2006-084532 |
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Mar 2006 |
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JP |
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Primary Examiner: Lee; Ping
Attorney, Agent or Firm: Mori & Ward, LLP
Claims
What is claimed is:
1. An active vibratory noise control apparatus comprising: a basic
signal generator configured to output a basic sine wave signal and
a basic cosine wave signal as basic signals, each of the basic sine
wave signal and the basic cosine wave signal having a frequency
that is based on a frequency of vibratory noise generated from a
vibratory noise source; an adaptive finite impulse response filter
configured to generate a control signal based on the basic cosine
wave signal or the basic sine wave signal using first to M-th
filter coefficients in order to cancel the vibratory noise
generated from the vibratory noise source where "M" is an integer
equal to or greater than 2 and is defined as a predetermined number
of taps of the adaptive finite impulse response filter, the
adaptive finite impulse response filter being configured to
respectively multiply first to M-th input signals sequentially
input from the basic signal generator by the first to M-th filter
coefficients to generate the control signal, the first input signal
being the latest among the first to M-th input signals, the M-th
reference signal being the oldest among the first to M-th input
signals; a vibratory noise cancelling device configured to generate
vibratory-noise canceling sound based on the control signal; an
error signal detector configured to output an error signal that is
based on a difference between the vibratory noise and the
vibratory-noise canceling sound; a reference signal generator
configured to sequentially generate a reference signal which is a
sum of a corrected basic cosine wave signal and a corrected basic
sine wave signal, the reference signal generator being configured
to correct the basic cosine wave signal and the basic sine wave
signal based on correction values regarding transfer
characteristics from the vibratory noise cancelling device to the
error signal detector with respect to frequencies of the basic
signals to obtain the corrected basic cosine wave signal and the
corrected basic sine wave signal; a buffer configured to accumulate
first to M-th reference signals sequentially generated in the
reference signal generator by a number equal to the predetermined
number of taps of the adaptive finite impulse response filter, the
first reference signal being the latest among the first to M-th
reference signals, the M-th reference signal being the oldest among
the first to M-th reference signals; and a filter coefficient
updating device configured to sequentially update the first to M-th
filter coefficients of the adaptive finite impulse response filter
so that the error signal is minimized based on the error signal and
the respective first to M-th reference signals accumulated in the
buffer.
2. The active vibratory noise control apparatus according to claim
1, wherein the basic signal generator is configured to output basic
signals having frequencies of a plurality of orders that are based
on the frequency of the vibratory noise, and wherein the reference
signal generator is configured to correct the basic signals output
from the basic signal generator based on correction values
corresponding to the basic signals having the frequencies of the
plurality of orders.
3. An active vibratory noise control apparatus comprising: a basic
signal generator configured to output a basic signal having a
frequency that is based on a frequency of vibratory noise generated
from a vibratory noise source, the basic signal generator including
a waveform data storage device configured to store, when outputting
the basic signal, instantaneous value data as waveform data
obtained at segment positions determined by dividing a sine wave or
cosine wave of one period by a predetermined number, the basic
signal generator being configured to read waveform data from the
waveform data storage device for each sampling to generate the
basic signal; an adaptive finite impulse response filter configured
to generate a control signal based on the basic signal using first
to M-th filter coefficients in order to cancel the vibratory noise
generated from the vibratory noise source where "M" is an integer
equal to or greater than 2 and is defined as a predetermined number
of taps of the adaptive finite impulse response filter, the
adaptive finite impulse response filter being configured to
respectively multiply first to M-th input signals sequentially
input from the basic signal generator by the first to M-th filter
coefficients to generate the control signal, the first input signal
being the latest among the first to M-th input signals, the M-th
reference signal being the oldest among the first to M-th input
signals; a vibratory noise cancelling device configured to generate
vibratory-noise canceling sound based on the control signal; an
error signal detector configured to output an error signal that is
based on a difference between the vibratory noise and the
vibratory-noise canceling sound; a reference signal generator
configured to correct the basic signal based on a correction value
regarding transfer characteristics from the vibratory noise
cancelling device to the error signal detector with respect to the
frequency of the basic signal and configured to sequentially
generate a corrected basic signal as a reference signal, the
reference signal generator including a correction data storage
device configured to store the correction value with respect to the
frequency of the basic signal when outputting the corrected basic
signal as the reference signal, the reference signal generator
being configured to refer to the frequency of the basic signal to
read the correction value from the correction data storage device
and configured to read the waveform data from a position that is
shifted by the correction value with respect to an address at which
the basic signal generator reads the waveform data from the
waveform data storage device to generate the reference signal; a
buffer configured to accumulate first to M-th reference signals
sequentially generated in the reference signal generator by a
number equal to the predetermined number of taps of the adaptive
finite impulse response filter, the first reference signal being
the latest among the first to M-th reference signals, the M-th
reference signal being the oldest among the first to M-th reference
signals; and a filter coefficient updating device configured to
sequentially update the first to M-th filter coefficients of the
adaptive finite impulse response filter so that the error signal is
minimized based on the error signal and the respective first to
M-th reference signals accumulated in the buffer.
4. The active vibratory noise control apparatus according to claim
3, wherein the basic signal generator is configured to output basic
signals having frequencies of a plurality of orders that are based
on the frequency of the vibratory noise, and wherein the reference
signal generator is configured to correct the basic signals output
from the basic signal generator based on correction values
corresponding to the basic signals having the frequencies of the
plurality of orders.
5. An active vibratory noise control apparatus comprising: basic
signal generating means for outputting a basic sine wave signal and
a basic cosine wave signal as basic signals, each of the basic sine
wave signal and the basic cosine wave signal having a frequency
that is based on a frequency of vibratory noise generated from a
vibratory noise source; adaptive finite impulse response filtering
means for generating a control signal based on the basic cosine
wave signal or the basic sine wave signal using first to M-th
filter coefficients in order to cancel the vibratory noise
generated from the vibratory noise source where "M" is an integer
equal to or greater than 2 and is defined as a predetermined number
of taps of the adaptive finite impulse response filter, the
adaptive finite impulse response filtering means being for
respectively multiplying first to M-th input signals sequentially
input from the basic signal generating means by the first to M-th
filter coefficients to generate the control signal, the first input
signal being the latest among the first to M-th input signals, the
M-th reference signal being the oldest among the first to M-th
input signals; vibratory noise cancelling means for generating
vibratory-noise canceling sound based on the control signal; error
signal detecting means for outputting an error signal that is based
on a difference between the vibratory noise and the vibratory-noise
canceling sound; reference signal generating means for sequentially
generating a reference signal which is a sum of a corrected basic
cosine wave signal and a corrected basic sine wave signal, the
reference signal generating means correcting the basic cosine wave
signal and the basic sine wave signal based on correction values
regarding transfer characteristics from the vibratory noise
cancelling means to the error signal detecting means with respect
to frequencies of the basic signals to obtain the corrected basic
cosine wave signal and the corrected basic sine wave signal; buffer
means for accumulating first to M-th reference signals sequentially
generated in the reference signal generating means by a number
equal to the predetermined number of taps of the adaptive finite
impulse response filtering means, the first reference signal being
the latest among the first to M-th reference signals, the M-th
reference signal being the oldest among the first to M-th reference
signals; and filter coefficient updating means for sequentially
updating the first to M-th filter coefficients of the adaptive
finite impulse response filtering means so that the error signal is
minimized based on the error signal and the respective first to
M-th reference signals accumulated in the buffer means.
6. The active vibratory noise control apparatus according to claim
5, wherein the basic signal generating means outputs basic signals
having frequencies of a plurality of orders that are based on the
frequency of the vibratory noise, and wherein the reference signal
generating means corrects the basic signals output from the basic
signal generating means based on correction values corresponding to
the basic signals having the frequencies of the plurality of
orders.
7. An active vibratory noise control apparatus comprising: basic
signal generating means for outputting a basic signal having a
frequency that is based on a frequency of vibratory noise generated
from a vibratory noise source, the basic signal generating means
including waveform data storage means for storing, when outputting
the basic signal, instantaneous value data as waveform data
obtained at segment positions determined by dividing a sine wave or
cosine wave of one period by a predetermined number, the basic
signal generating means reading waveform data from the waveform
data storage means for each sampling to generate the basic signal;
adaptive finite impulse response filtering means for generating a
control signal based on the basic signal using first to M-th filter
coefficients in order to cancel the vibratory noise generated from
the vibratory noise source where "M" is an integer equal to or
greater than 2 and is defined as a predetermined number of taps of
the adaptive finite impulse response filter, the adaptive finite
impulse response filtering means being for respectively multiplying
first to M-th input signals sequentially input from the basic
signal generating means by the first to M-th filter coefficients to
generate the control signal, the first input signal being the
latest among the first to M-th input signals, the M-th reference
signal being the oldest among the first to M-th input signals;
vibratory noise cancelling means for generating vibratory-noise
canceling sound based on the control signal; error signal detecting
means for sequentially generating an error signal that is based on
a difference between the vibratory noise and the vibratory-noise
canceling sound; reference signal generating means for correcting
the basic signal based on a correction value regarding transfer
characteristics from the vibratory noise cancelling means to the
error signal detecting means with respect to the frequency of the
basic signal and for sequentially generating a corrected basic
signal as a reference signal, the reference signal generating means
including correction data storage means for storing the correction
value with respect to the frequency of the basic signal when
outputting the corrected basic signal as the reference signal, the
reference signal generating means referring to the frequency of the
basic signal to read the correction value from the correction data
storage device and reading the waveform data from a position that
is shifted by the correction value with respect to an address at
which the basic signal generating means reads the waveform data
from the waveform data storage means to generate the reference
signal; buffer means for accumulating first to M-th reference
signals sequentially generated in the reference signal generating
means by a number equal to the predetermined number of taps of the
adaptive finite impulse response filtering means, the first
reference signal being the latest among the first to M-th reference
signals, the M-th reference signal being the oldest among the first
to M-th reference signals; and filter coefficient updating means
for sequentially updating the first to M-th filter coefficients of
the adaptive finite impulse response filtering means so that the
error signal is minimized based on the error signal and the
respective first to M-th reference signals accumulated in the
buffer means.
8. The active vibratory noise control apparatus according to claim
6, wherein the basic signal generating means outputs basic signals
having frequencies of a plurality of orders that are based on the
frequency of the vibratory noise, and wherein the reference signal
generating means corrects the basic signals output from the basic
signal generating means based on correction values corresponding to
the basic signals having the frequencies of the plurality of
orders.
Description
CROSS REFERENCES TO RELATED APPLICATIONS
The present application claims priority under 35 U.S.C. .sctn.119
to Japanese Patent Application No. 2009-179122, filed Jul. 31,
2009, entitled "ACTIVE VIBRATORY NOISE CONTROL APPARATUS." The
contents of this application are incorporated herein by reference
in their entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an active vibratory noise control
apparatus.
2. Description of the Related Art
In the related art, active vibratory noise control apparatuses for
adaptively reducing vibratory noise in a passenger compartment of a
vehicle in accordance with a control signal having the frequency of
vibratory noise of an engine are proposed in, for example, Japanese
Patents No. 3843082 ([0012], [0013], [0014], [0016]) and No.
4074612 ([0012], [0015], [0016], [0169]).
In the active vibratory noise control apparatus proposed in
Japanese Patent No. 3843082, a basic signal generating means
generates basic signals (a basic sine wave signal and a basic
cosine wave signal) having frequencies that are based on the
frequency of vibratory noise generated from a vibratory noise
source, and a first adaptive notch filter generates a first control
signal based on the generated basic cosine wave signal. Further, a
second adaptive notch filter generates a second control signal
based on the generated basic sine wave signal. Vibratory-noise
canceling sound is generated from a speaker based on a sum signal
representing the sum of the first control signal and the second
control signal to cancel the vibratory noise.
In the cancellation of vibratory noise, an error signal that is
based on the difference between the vibratory noise and the
vibratory-noise canceling sound is detected using a microphone, and
a signal produced by subtracting the product of a sine correction
value based on the sine value of the phase characteristics in the
signal transfer characteristics at the frequencies of the basic
signals from the speaker to the microphone and the basic sine wave
signal from the product of a cosine correction value based on the
cosine value of the phase characteristics and the basic cosine wave
signal is generated as a first reference signal. Further, a signal
produced by summing the product of the sine correction value and
the basic cosine wave signal and the product of the cosine
correction value and the basic sine wave signal is generated as a
second reference signal. A filter coefficient updating means
sequentially updates the filter coefficients of the first and
second adaptive notch filters so that the error signal can be
minimized based on the error signal and the first and second
reference signals. Thus, the vibratory noise is canceled by the
vibratory-noise canceling sound output from the speaker.
The active vibratory noise control apparatus proposed in Japanese
Patent No. 4074612 has a specific and simple configuration of a
basic signal generating means and a reference signal generating
means. In the apparatus, the basic signal generating means includes
a waveform data storage means for storing, as waveform data,
instantaneous value data obtained at individual segment positions
determined by dividing the sine wave of one period by a
predetermined number. Waveform data is read in sequence from the
waveform data storage means for each sampling to generate a basic
sine wave signal, and waveform data is read in sequence from
addresses of the waveform data storage means, which are shifted by
a quarter period with respect to the addresses at which the basic
sine wave signal is read, to generate a basic cosine wave
signal.
Further, the reference signal generating means includes a
correction data storage means for storing, when correcting the
basic sine wave signal and the basic cosine wave signal based on
correction values indicating the phase characteristics in the
transfer characteristics from the speaker to the microphone with
respect to the frequencies of the basic signals and when outputting
the corrected signals as reference signals, the correction values
with respect to the frequencies of the basic signals, and is
configured to generate a reference signal by referring to the
frequencies of the basic signals, reading the correction values
from the correction data storage means, and reading waveform data
from the addresses that are shifted by the correction values with
respect to the addresses at which the waveform data is read from
the waveform data storage means.
In the technique disclosed in Japanese Patent No. 3843082, the
correction values include a sine correction value that is based on
a phase-delayed sine value and a cosine correction value that is
based on a phase-delayed cosine value in the signal transfer
characteristics of vibratory sound from the speaker to the
microphone, which correspond to the frequencies of the basic
signals, and are stored in advance in the storage means in
correspondence with the frequencies of the basic signals. The
correction values are read in correspondence with the frequencies
of the basic signals, and the read cosine correction value and sine
correction value are multiplied by the basic cosine wave signal and
the basic sine wave signal. The multiplication results are summed
to obtain a reference signal. Thus, the amount of computation
required to obtain a reference signal is significantly smaller than
that required when a FIR filter is used, and an active vibratory
noise control apparatus can be manufactured inexpensively.
In the technique disclosed in Japanese Patent No. 4074612, address
shift values that are based on the phase characteristics in the
signal transfer characteristics from the speaker to the microphone
are stored in advance in the correction data storage means in
accordance with the frequencies of basic signals, and waveform data
read from an address that is shifted by an address shift value read
from the correction data storage means with respect to address data
for reading a basic cosine wave signal and a basic sine wave signal
from the waveform data storage means by referring to the
frequencies of the basic signals is used as first and second
reference signals. Thus, the signal transfer characteristics can be
optimally modeled, and first and second reference signals can be
obtained with a smaller amount of computation than that required
when a FIR filter is used. In addition, vibratory noise can be
canceled with sufficient convergence.
As described above, Japanese Patents No. 3843082 and No. 4074612
describe that with the use of an adaptive FIR filter instead of an
adaptive notch filter, a large computational load is required to
generate a reference signal and a processor with high computation
performance, such as a digital signal processor, is required.
SUMMARY OF THE INVENTION
According to one aspect of the present invention, an active
vibratory noise control apparatus includes a basic signal
generator, an adaptive finite impulse response filter, a vibratory
noise cancelling device, an error signal detector, a reference
signal generator, a buffer, and a filter coefficient updating
device. The basic signal generator is configured to output a basic
sine wave signal and a basic cosine wave signal as basic signals.
Each of the basic sine wave signal and the basic cosine wave signal
has a frequency that is based on a frequency of vibratory noise
generated from a vibratory noise source. The adaptive finite
impulse response filter is configured to output a control signal
based on the basic cosine wave signal or the basic sine wave signal
in order to cancel the vibratory noise generated from the vibratory
noise source. The vibratory noise cancelling device is configured
to generate vibratory-noise canceling sound based on the control
signal. The error signal detector is configured to output an error
signal that is based on a difference between the vibratory noise
and the vibratory-noise canceling sound. The reference signal
generator is configured to output a reference signal which is a sum
of a corrected basic cosine wave signal and a corrected basic sine
wave signal. The reference signal generator corrects the basic
cosine wave signal and the basic sine wave signal based on
correction values regarding transfer characteristics from the
vibratory noise cancelling device to the error signal detector with
respect to frequencies of the basic signals to obtain the corrected
basic cosine wave signal and the corrected basic sine wave signal.
The buffer is configured to accumulate a number of reference
signals corresponding to a number of taps of the adaptive finite
impulse response filter. The filter coefficient updating device is
configured to sequentially update filter coefficients of the
adaptive finite impulse response filter so that the error signal is
minimized based on the error signal and the reference signals
accumulated in the buffer.
According to another aspect of the present invention, an active
vibratory noise control apparatus includes a basic signal
generator, an adaptive finite impulse response filter, a vibratory
noise cancelling device, an error signal detector, a reference
signal generator, a buffer, and a filter coefficient updating
device. The basic signal generator is configured to output a basic
signal having a frequency that is based on a frequency of vibratory
noise generated from a vibratory noise source. The basic signal
generator includes a waveform data storage device configured to
store, when outputting the basic signal, instantaneous value data
as waveform data obtained at segment positions determined by
dividing a sine wave or cosine wave of one period by a
predetermined number. The basic signal generator is configured to
read waveform data from the waveform data storage device for each
sampling to generate the basic signal. The adaptive finite impulse
response filter is configured to output a control signal based on
the basic signal in order to cancel the vibratory noise generated
from the vibratory noise source. The vibratory noise cancelling
device is configured to generate vibratory-noise canceling sound
based on the control signal. The error signal detector is
configured to output an error signal that is based on a difference
between the vibratory noise and the vibratory-noise canceling
sound. The reference signal generator is configured to correct the
basic signal based on a correction value regarding transfer
characteristics from the vibratory noise cancelling device to the
error signal detector with respect to the frequency of the basic
signal. The reference signal generator is configured to output the
corrected basic signal as a reference signal. The reference signal
generator includes a correction data storage device configured to
store the correction value with respect to the frequency of the
basic signal when outputting the corrected basic signal as the
reference signal. The reference signal generator is configured to
refer to the frequency of the basic signal to read the correction
value from the correction data storage device and configured to
read the waveform data from a position that is shifted by the
correction value with respect to an address at which the basic
signal generator reads the waveform data from the waveform data
storage device to generate the reference signal. The buffer is
configured to accumulate a number of reference signals
corresponding to a number of taps of the adaptive finite impulse
response filter. The filter coefficient updating device is
configured to sequentially update filter coefficients of the
adaptive finite impulse response filter so that the error signal is
minimized based on the error signal and the reference signals
accumulated in the buffer.
BRIEF DESCRIPTION OF THE DRAWINGS
A more complete appreciation of the invention and many of the
attendant advantages thereof will be readily obtained as the same
becomes better understood by reference to the following detailed
description when considered in connection with the accompanying
drawings, wherein:
FIG. 1 is a schematic diagram of a vehicle having incorporated
therein an active vibratory noise control apparatus according to
first to sixth embodiments of the present invention;
FIG. 2 is a block diagram illustrating a detailed configuration of
the active vibratory noise control apparatus according to the first
embodiment of the present invention illustrated in FIG. 1;
FIG. 3 is a diagram depicting a waveform data storage device that
stores waveform data of the sine wave of one period;
FIG. 4A is a schematic diagram illustrating a method for generating
a basic sine wave signal, and FIG. 4B is a schematic diagram
illustrating a method for generating a basic cosine wave
signal;
FIG. 5 is a diagram illustrating a measured value table of signal
transfer characteristics with respect to a control frequency in a
passenger compartment space between a speaker and a microphone
provided in a vehicle;
FIG. 6 is a diagram illustrating a correction data storage device
that stores a calculated cosine correction value and sine
correction value corresponding to a control frequency;
FIG. 7 is a characteristic diagram before and after cancellation of
muffled engine noise in a case where an active vibratory noise
control apparatus according to the first embodiment of the present
invention is used in a vehicle;
FIG. 8 is a block diagram illustrating a detailed configuration of
the active vibratory noise control apparatus according to the
second embodiment of the present invention illustrated in FIG.
1;
FIG. 9 is a block diagram illustrating a detailed configuration of
the active vibratory noise control apparatus according to the third
embodiment of the present invention illustrated in FIG. 1;
FIG. 10 is a diagram depicting an example of content of a
correction data storage device according to the third embodiment of
the present invention;
FIG. 11 is a block diagram illustrating a detailed configuration of
the active vibratory noise control apparatus according to the
fourth embodiment of the present invention illustrated in FIG.
1;
FIG. 12 is a block diagram illustrating a detailed configuration of
the active vibratory noise control apparatus according to the fifth
embodiment of the present invention illustrated in FIG. 1; and
FIG. 13 is a block diagram illustrating a detailed configuration of
the active vibratory noise control apparatus according to the sixth
embodiment of the present invention illustrated in FIG. 1.
DESCRIPTION OF THE EMBODIMENTS
Embodiments of the present invention will now be described with
reference to the drawings.
FIG. 1 schematically illustrates the configuration of a vehicle 1
having any of active vibratory noise control apparatuses 10, 10A,
10B, 10C, 10D, and 10E according to first to sixth embodiments of
the present invention.
The active vibratory noise control apparatus 10 (10A, 10B, 10C,
10D, 10E) basically has the following configuration: Engine pulses
4 output from an engine controller 3 that controls an engine 2
(vibratory noise source) of the vehicle 1 are input to an active
vibratory noise control device 12 (12A, 12B, 12C, 12D, 12E) (active
vibration control means) configured using a microcomputer that
cooperates with a speaker 6 (vibratory noise cancelling means) and
a microphone 8 (error signal detecting means), and the speaker 6 is
driven by the output of an adaptive FIR filter 20 whose filter
coefficients are adaptively controlled so that the output from the
microphone 8 can be minimized. Further, vibratory noise (muffled
engine noise) at the position (listening position) of the
microphone 8 inside the compartment of the vehicle 1 is cancelled
using vibratory-noise canceling sound output from the speaker
6.
For example, the speaker 6 may be provided at a predetermined
position behind the backseat of the vehicle 1, and the microphone 8
may be provided on a passenger compartment ceiling at the center of
the passenger compartment in the vehicle 1.
FIG. 2 is a block diagram illustrating a detailed configuration of
the active vibratory noise control device 12 included in the active
vibratory noise control apparatus 10 according to the first
embodiment of the present invention.
As illustrated in FIG. 2, the active vibratory noise control device
12 basically includes a frequency detector 16, a basic signal
generator 18 (basic signal generating means), an adaptive FIR
filter 20, a reference signal generator 22 (reference signal
generating means or correcting means), a buffer 24, and a filter
coefficient updating device 26 (filter coefficient updating means
or LMS algorithm computation device).
The frequency detector 16, which may also serve as a sampling pulse
generator, detects the frequency of gas combustion in the engine 2
from the frequency of the engine pulses 4 as a control frequency f
that is the frequency of vibratory noise, and supplies the control
frequency f to the basic signal generator 18 and the reference
signal generator 22. The frequency detector 16 also generates
sampling pulses (timing signal) having sampling periods of the
active vibratory noise control device 12, and supplies the sampling
pulses to the individual devices. Here, it is assumed that sampling
pulses having a sampling frequency fs that is fixed to, for
example, 3 [kHz] and having sampling intervals (sampling periods)
ts of 1/3000 [s] are supplied to the individual devices.
Muffled engine noise taken as vibratory noise NS input to the
microphone 8 is vibration radiation noise caused by an excitation
force being generated by the rotation of the engine 2 and
transferred to the vehicle body. The muffled engine noise is
therefore vibratory noise having a noticeable periodicity
synchronous with the rotational speed of the engine 2. For example,
a 4-cycle 4-cylinder engine allows excitation of vibration based on
the engine due to the variation in torque generated by gas
combustion that occurs every one-half rotation of the output shaft
of the engine, which causes the generation of the vibratory noise
NS in the passenger compartment.
Therefore, a 4-cycle 4-cylinder engine causes a large amount of
vibratory noise NS called rotational second-order component having
a frequency that is twice as high as the rotational speed of the
output shaft of the engine (engine rotational speed Ne [rpm]).
Thus, as described above, the frequency detector 16 outputs the
detected frequency from the engine pulses 4, that is, the frequency
that is twice as high as the engine rotational speed Ne, as a
control frequency f [Hz] {f=(Ne/60).times.2} that is a vibratory
noise frequency. The control frequency f is equal to the frequency
of the vibratory noise NS to be canceled. The control frequency f
is hereinafter also referred to simply as "frequency f".
In practice, if the second-order component is suppressed, then, the
vibratory noise of the fourth-order component, sixth-order
component, and further higher-order components may be heard louder.
Preferably, these high-order components are also suppressed, which
will be described below.
The basic signal generator 18 includes a waveform data storage
device 30, a basic cosine wave signal generation device 31, and a
basic sine wave signal generation device 32.
As schematically illustrated in FIG. 3, the waveform data storage
device 30 stores instantaneous value data indicating instantaneous
values obtained at positions determined by evenly dividing the
waveform of the sine wave of one period in the time axis direction
by a given number N (in this embodiment, N=3000 since the
resolution is 1 [Hz] for ease of understanding), as waveform data
for each address i(n) (i(n)=0, 1, 2, . . . , N-1) where the address
i(n) is in the range of 0 to the given number minus 1, i.e., N-1
(N-1=2999).
An amplitude A is a positive real number, and the waveform data at
the address i(n)=i is given by A sin {2.pi..times.i/N}.
In this manner, the waveform data storage device 30 is configured
to divide the sine wave of one cycle in the time direction into N
segments which are sampled and to store the data of quantized
instantaneous values of the sine wave at the individual sampling
points, as waveform data, at the positions of the corresponding
addresses i(n). Alternatively, instead of using the sine wave, the
cosine wave of one cycle may be divided in the time direction into
N segments which are sampled, and the data of quantized
instantaneous values of the cosine wave at the individual sampling
points may be stored as waveform data at the positions of the
corresponding addresses i(n).
A method in which the basic signal generator 18 generates basic
signals including a basic cosine wave signal cos 2.pi.ft
(hereinafter also referred to simply as "cos") and a basic sine
wave signal sin 2.pi.ft (hereinafter also referred to simply as
"sin") will now be described with reference to FIGS. 3, 4A, and 4B.
Here, in FIGS. 4A and 4B, it is assumed that an index n is an
integer of 0 or more and increases by +1 for each of the sampling
pulses. However, after n=2999, the index n of the corresponding
sampling pulse is reset to 0.
FIG. 4A is a schematic diagram describing a process of generating
the basic sine wave signal sin, and FIG. 4B is a schematic diagram
describing a process of generating the basic cosine wave signal
cos.
As described above, the address i(n) is given by i(n)=0, 1, 2, . .
. , N-1=0, 1, 2, . . . , 2999, and the number of shifts in a
quarter period is given by N/4=750.
The basic sine wave signal generation device 32 generates the basic
sine wave signal sin illustrated in FIG. 4A by reading the waveform
data in sequence from the waveform data storage device 30 while
adding the address i(n) by a number corresponding to the control
frequency f (when the control frequency f is 40 [Hz], then 40) for
each sampling pulse generated by the frequency detector 16 as given
by Equation (1) below.
Specifically, since the sampling intervals are given by 1/fs=ts=
1/3000 (=1/N) [s], the basic sine wave signal generation device 32
in the basic signal generator 18 specifies, for each sampling
pulse, as given by Equation (1) below, the read address i(n) of the
waveform data storage device 30 at an address interval iint that is
based on the control frequency f.
The address interval iint is given by
iint=N.times.f.times.ts=3000.times.f.times. 1/3000=f. Therefore,
the read address i(n) at a certain timing is given by:
i(n)=i(n-1)+iint=i(n-1)+f (1) where if i(n)>2999 (=N-1), then
i(n)=i(n-1)+f-3000.
For example, when the control frequency f is given by f=40 [Hz]
(when the engine rotational speed Ne [rpm] is given by
Ne=f.times.60/2=40.times.60/2=1200 [rpm]), after the start of
control, waveform data at the addresses i(n) corresponding to the
indices n of the addresses i(n)=0, 40, 80, 120, . . . , 2960, 0, .
. . is read in sequence for each sampling pulse, that is, for each
sampling interval ts= 1/3000 [s], and the basic sine wave signal
sin of 40 [Hz] is generated. Further, when the control frequency f
given by f=80 [Hz] (when the engine rotational speed Ne [rpm] is
given by Ne=f.times.60/2=80.times.60/2=2400 [rpm]), after the start
of control, waveform data at the addresses i(n) corresponding to
the indices n of the addresses i(n)=0, 80, 160, . . . , 2960, 40, .
. . is read in sequence for each sampling pulse, that is, for each
sampling interval ts= 1/3000 [s], and the basic sine wave signal
sin of 80 [Hz] is generated.
Similarly, as given by Equation (2) below, the basic cosine wave
signal generation device 31 specifies the address that is shifted
(summed) by a quarter period (N/4) with respect to the read address
i(n) {on the left side of Equation (2)} of the basic sine wave
signal sin specified by the basic sine wave signal generation
device 32, as the read address i(n) {on the left side of Equation
(2)} of the basic cosine wave signal cos: i(n)=i(n)+N/4=i(n)+750
(2) where if i(n)>2999 (=N-1), then i(n)=i(n)+750-3000.
Therefore, the basic cosine wave signal generation device 31
generates the basic cosine wave signal cos illustrated in FIG. 4B
by reading the waveform data in sequence from the waveform data
storage device 30 at the address intervals corresponding to the
control frequency f for each sampling pulse generated by the
frequency detector 16, starting from the address that is shifted by
a quarter period with respect to the read start address.
For example, when the control frequency f is given by f=40 [Hz]
(when the engine rotational speed Ne [rpm] is given by
Ne=f.times.60/2=40.times.60/2=1200 [rpm]), after the start of
control, waveform data at the addresses i(n) corresponding to the
indices n of the addresses i(n)=750, 790, 830, 870, . . . 2990, 30,
70, . . . , 710, 750, . . . is read in sequence for each sampling
pulse, that is, for each sampling interval tc= 1/3000 [s], and the
basic cosine wave signal cos of 40 [Hz] is generated. Further, when
the control frequency f is given by f=80 [Hz]
(Ne=f.times.60/2=80.times.60/2=2400 [rpm]), after the start of
control, waveform data at the addresses i(n) corresponding to the
indices n of the addresses i(n)=750, 830, 910, . . . , 2990, 70,
150, . . . , 710, 790, . . . is read in sequence for each sampling
pulse, that is, for each sampling interval tc= 1/3000 [s], and the
basic cosine wave signal cos of 80 [Hz] is generated.
As illustrated in FIG. 2, the basic cosine wave signal cos
generated by the basic cosine wave signal generation device 31 in
the manner described above is input to the adaptive FIR filter 20.
Further, the basic cosine wave signal cos and the basic sine wave
signal sin generated by the basic cosine wave signal generation
device 31 and the basic sine wave signal generation device 32,
respectively, are input to the reference signal generator 22.
The adaptive FIR filter 20 filters the basic cosine wave signal cos
to generate a control signal Sc, and outputs the control signal Sc
to a digital-to-analog (D/A) converter 40.
Here, as illustrated in FIG. 2, the adaptive FIR filter 20 has M
taps of filter coefficients h=h0, h1, . . . , hM-1. The number of
taps M may be determined with confirmation of the effect of
control.
In this case, the transfer function H(z) of the adaptive FIR filter
20 is represented by Equation (3) as follows:
H(z)=h0+h1z.sup.-1+h2z.sup.-2+ . . . +hM-1z.sup.-(M-1) (3) where
the delay time T of each element z.sup.-1 corresponds to the
sampling interval (sampling period) ts= 1/3000 [s].
Each of (M-1) elements z.sup.-1 is configured using, for example,
first-in first-out (FIFO) memories (in terms of memory, referred to
as "buffers z.sup.-1"), and data is transferred for each sampling
pulse from a left buffer z.sup.-1 to a right buffer z.sup.-1. In
this case, the leftmost buffer z.sup.-1 stores the value of the
latest basic cosine wave signal cos generated by the basic signal
generator 18, and the data stored in the rightmost buffer z.sup.-1
is deleted.
The D/A converter 40 converts a digital control signal Sc
{Sc=H(z).times.cos 2.pi.ft} into an analog control signal Sc. The
control signal Sc is input to the speaker 6 through a low-pass
filter (not illustrated) and an amplifier 42.
The speaker 6 outputs vibratory-noise canceling sound SS
corresponding to the control signal Sc. The vibratory-noise
canceling sound SS output from the speaker 6 propagates in a
passenger compartment space (sound field), and is input to the
microphone 8.
The active vibratory noise control device 12 executes a noise
reduction control process so that the amplitude and phase of the
vibratory-noise canceling sound SS at the position of the
microphone 8 can have the same amplitude as and opposite phase to
the vibratory noise NS.
In order to execute the noise reduction control process, the
difference between the vibratory noise NS and the vibratory-noise
canceling sound SS is detected as an error signal e (e=NS-SS) by
the microphone 8, and the detected error signal e, which is an
analog signal, is input to the filter coefficient updating device
26 as a digital error signal e through an analog-to-digital (A/D)
converter 46.
The reference signal generator 22 includes a correction data
storage device 52, a cosine correction value setting device 54
serving as a multiplier, a sine correction value setting device 56
serving as a multiplier, and an adder 58.
The correction data storage device 52 stores a cosine correction
value C(f) that is based on a phase-delayed cosine value in signal
transfer characteristics in the passenger compartment space between
the speaker 6 and the microphone 8 in correspondence with the
control frequency f. The correction data storage device 52 also
stores a sine correction value D(f) that is based on a
phase-delayed sine value in the signal transfer characteristics in
correspondence with the control frequency f. The correction data
storage device 52 is accessed by sampling pulses output from the
frequency detector 16, and the cosine correction value C(f) and
sine correction value D(f) corresponding to the control frequency f
are set in the cosine correction value setting device 54 and the
sine correction value setting device 56, respectively.
A numerical example of the cosine correction value C(f) and sine
correction value D(f) stored in advance in the correction data
storage device 52 will now be described.
FIG. 5 illustrates a measured value table 50 of the gain G and
phase delay .phi. in the signal transfer characteristics with
respect to each control frequency f in the passenger compartment
space between the speaker 6 and the microphone 8 provided in the
vehicle 1. The gain G is expressed in [dB], and the phase delay
.phi. is expressed in angle [.degree.].
Here, referring to the configuration of the reference signal
generator 22 illustrated in FIG. 2. it is found that a reference
signal r is obtained by Equation (4) (vector addition) and Equation
(5) as follows:
.times..times..times..times..times..times..pi..times..times..function..ti-
mes..times..times..times..pi..times..times..times..times.
.times..times..times..pi..times..times..function..times..times..function.-
.times..pi..times..times..PHI..times. ##EQU00001##
From Equation (5), the cosine correction value C(f) and the sine
correction value D(f) can be calculated for each control frequency
f on the basis of the measured values of the gain G and phase delay
.phi. illustrated in FIG. 5.
FIG. 6 illustrates an example of the correction data storage device
52 in which cosine correction values C(f) and sine correction
values D(f) calculated from the gain G and phase delay .phi. of the
measured value table 50, which correspond to the control
frequencies f, are stored.
A reference signal r {r=C(f)cos 2 .pi.ft+D(f)sin 2.pi.ft} generated
for each sampling pulse by the reference signal generator 22, which
is configured using the cosine correction value setting device 54,
the sine correction value setting device 56, and the adder 58, is
stored in the buffer 24 for each sampling pulse.
The buffer 24 is configured using a FIFO memory having M storage
areas the number of which is the same as the number of taps M of
the adaptive FIR filter 20.
For the delay time T described above, that is, for each sampling
pulse, the latest reference signal r generated by the reference
signal generator 22 is stored as a reference signal r0 in the top
storage area in the buffer 24 in FIG. 2, and the reference signal r
is transferred from the top storage area to the lower storage area.
The oldest reference signal rM-1 is stored in the bottom storage
area in the buffer 24, and the data stored in the bottom storage
area is deleted.
Next, the filter coefficient updating device 26 calculates the
filter coefficients h0, h1, . . . , hM-1 of the adaptive FIR filter
20 using Equation (6) below, which is known in the technical field,
using the Least Mean Square (LMS) algorithm so that the square of
the error signal e, i.e., e.sup.2, can be minimized: h0=h0-.mu.er0
h1=h1-.mu.er1 hM-1=(hM-1)-.mu.e(rM-1) (6) where .mu. is a step-size
parameter.
Specifically, the subsequent filter coefficients h0, h1, . . . ,
hM-1 on the left side can be determined by subtracting .mu.er0,
.mu.er1, . . . , .mu.e(rM-1) from the current filter coefficients
h0, h1, . . . , hM-1 on the right side, respectively.
In the active vibratory noise control apparatus 10 according to the
first embodiment described above, therefore, since the adaptive FIR
filter 20 is used as an adaptive filter that generates a control
signal Sc, a reference signal r can be determined by the reference
signal generator 22 using a product-sum operation including two
multiplications and one addition. Thus, the computational load
required to generate the reference signal r can be reduced.
In FIG. 7, the solid line represents a result obtained in the
vehicle 1 having the active vibratory noise control apparatus 10
incorporated therein, by generating a reference signal r using a
cosine correction value C(f) and a sine correction value D(f) and
canceling vibratory noise NS taken as muffled engine noise by
vibratory-noise canceling sound SS generated through the adaptive
FIR filter 20, with respect to the engine rotational speed Ne. It
is found that the muffled engine noise is sufficiently canceled in
contrast with no cancellation of muffled engine noise indicated by
the broken line in FIG. 7.
FIG. 8 is a block diagram illustrating a detailed configuration of
the active vibratory noise control apparatus 10A according to the
second embodiment of the present invention.
As described above, when vibratory noise NS called rotational
second-order component having a frequency that is twice as high as
the engine rotational speed Ne, that is, the control frequency f
described above, is suppressed, the vibratory noise NS of the
fourth-order component, sixth-order component, and the like may
become noticeable at the position of the microphone 8. Here, for
ease of understanding, it is assumed that the second-order,
fourth-order, and sixth-order components become noticeable.
It is now assume that the frequency components of the order p to be
controlled are represented by f1=f.times.p1=f.times.1 (second-order
component), f2=f.times.p2=f.times.2 (fourth-order component), and
f3=f.times.p3=f.times.3 (sixth-order component).
A frequency detector 16A outputs, in addition to the detected
control frequency f=f1, the control frequencies f2 and f3 obtained
by multiplying the control frequency f by two and three,
respectively.
In this case, basic cosine wave signal generation devices 31, 31a,
and 31b and basic sine wave signal generation devices 32, 32a, and
32b of a basic signal generator 18A, can generate individual basic
signals given by Expression (7) below by reading waveform data at
the address i(n) and the address i(n) that is shifted by a quarter
period for each sampling pulse from the waveform data storage
device 30 while skipping a number of addresses i(n) corresponding
to the control frequencies f1, f2, and f3: cos 2.pi.f1t, sin
2.pi.f1t, cos 2.pi.f2t, sin 2.pi.f2t, cos 2.pi.f3t, sin 2.pi.f3t
(7)
An adder 33 generates a basic cosine wave signal cos=cos
2.pi.f1t+cos 2.pi.f2t+cos 2.pi.f3t, and inputs the basic cosine
wave signal cos to an adaptive FIR filter 20.
A correction data storage device 52A configured to generate a
reference signal r stores cosine correction values C(f)=C(f1),
C(f2), C(f3) and sine correction values D(f)=D(f1), D(f2), D(f3)
calculated from the gain G and phase delay .phi. in a measured
value table (an extended table of the measured value table 50 in
which the measurement frequency range is extended to the
high-frequency side), which correspond to the control frequencies f
(f=f1, f2, f3).
For the delay time T described above, that is, for each sampling
interval ts, the reference signal r represented by Equation (8)
corresponding to the number of taps M of the adaptive FIR filter 20
is generated by a reference signal generator 22A including cosine
correction value setting devices 54, 54a, and 54b, sine correction
value setting devices 56, 56a, and 56b, and adders 58, 58a, 58b,
and 59, and is stored as a reference signal r0, r1, . . . , rM-1 in
each storage area of the buffer 24 having M storage areas (memory
addresses) illustrated in FIG. 8: r=C(f1)cos 2.pi.f1t+D(f1)sin
2.pi.f1t+C(f2)cos 2.pi.f2t+D(f2)sin 2.pi.f2t+C(f3)cos
2.pi.f3t+D(f3)sin 2.pi.f3t (8)
Subsequently, a filter coefficient updating device 26 calculates
the individual filter coefficients h0, h1, . . . , hM-1 of the
adaptive FIR filter 20 in a manner similar to that described
above.
In the active vibratory noise control apparatus 10A according to
the second embodiment of the present invention, since the adaptive
FIR filter 20 is used as an adaptive filter that generates a
control signal Sc, reference signals r corresponding to components
of a plurality of orders, here, components of three orders (second
order, fourth order, and sixth order), are determined using a
product-sum operation including six multiplications and five
additions. The computational load required to generate the
reference signals r can therefore be significantly reduced.
FIG. 9 is a block diagram illustrating the configuration of the
active vibratory noise control apparatus 10B according to the third
embodiment of the present invention.
A basic signal generator 18B that generates a basic cosine wave
signal cos includes a frequency detector 16, an address setter 60,
and a waveform data storage device 30. The address setter 60 can
generate a basic cosine wave signal cos by reading waveform data in
sequence from the waveform data storage device 30 at read addresses
i(n) {an address i(n) is hereinafter simply referred to as an
"address i"} given in Equation (2). The generated basic cosine wave
signal cos is input to an adaptive FIR filter 20.
Here, a correction data storage device 52A stores, as illustrated
in FIG. 10, correction values (corrected address values) ic at
addresses, which are calculated using Equations (9) and (10) below,
in correspondence with the gain G and the phase delay .phi.
corresponding to the control frequencies f, which are based on the
measured value table 50 illustrated in FIG. 5: When .phi..gtoreq.0,
then ic=(.phi./360).times.f (9) When .phi.<0, then
ic=f+(.phi./360).times.f (10)
A reference signal generator 22B reads waveform data from the
waveform data storage device 30 at address i+ic obtained by adding
the corrected address value ic to the address i using an address
corrector 62, thereby generating a reference signal cos
{2.pi.ft+.phi.(f)} while taking account of the phase delay .phi. at
the control frequency f in the passenger compartment space from a
speaker 6 to a microphone 8.
Further, the reference signal generator 22B multiplies the
generated reference signal cos {2.pi.ft+.phi.(f)} by the gain G
that is simultaneously read from the correction data storage device
52A and that is set in a gain setter 64, thereby generating a
reference signal r with the phase delay .phi. and the gain G taken
into account as r=Gcos {2.pi.ft+.phi.(f)}. In the active vibratory
noise control device 12B included in the active vibratory noise
control apparatus 10B according to the third embodiment of the
present invention, the reference signal generator 22B (reference
signal generating means) is configured using the correction data
storage device 52A, the address corrector 62, the waveform data
storage device 30, and the gain setter 64.
The generated reference signal r=Gcos {2.pi.ft+.phi.(f)} is stored
in each storage area of a buffer 24 serving as a FIFO memory having
M storage areas (memory addresses), for each delay time T described
above, as reference signals r0, r1, . . . , rM-1.
Subsequently, a filter coefficient updating device 26 calculates
the individual filter coefficients h0, h1, . . . , hM of the
adaptive FIR filter 20 in a manner similar to that described
above.
In the active vibratory noise control apparatus 10B according to
the third embodiment of the present invention, since the adaptive
FIR filter 20 is used as an adaptive filter that generates a
control signal Sc, a reference signal r is generated by reading
waveform data at the address value i+ic that is shifted by the
correction value of the address (corrected address value or address
shift value) is corresponding to the correction value (the gain G
and the phase delay .phi.) corresponding to the transfer
characteristics in the passenger compartment space of the control
frequency f with respect to the address i at which the basic cosine
wave signal cos 2.pi.ft is generated. Thus, the computational load
required to generate the reference signals r can be significantly
reduced.
More specifically, the active vibratory noise control apparatus 10B
according to the third embodiment of the present invention is the
active vibratory noise control apparatus 10B that includes the
adaptive FIR filter 20 having filter coefficients h0, h1, . . . ,
hM-1 of M taps, in which the reference signal generator 22B
generates a reference signal r=G(f).times.cos {2.pi.ft+.phi.(f)} by
reading a correction value {G(f), ic} from the correction data
storage device 52A that stores correction values {address shift
values ic corresponding to the gain G(f) and the phase .phi.: see
FIG. 10} regarding the transfer characteristics {G(f), .phi.},
which correspond to the frequency of the basic cosine wave signal
cos 2.pi.ft having a control frequency f that is based on the
vibratory noise frequency (namely, which correspond to the control
frequency f), and by correcting the basic signal cos 2.pi.ft, and
accumulates, in the buffer 24, a number M of reference signals r
(r0, r1, . . . , rM-1) corresponding to the number of taps M of the
FIR filter 20.
The reference signals r (r0, r1, . . . , rM-1) are used for
updating and computation of the filter coefficients h0, h1, . . . ,
hM-1 of the adaptive FIR filter 20. Since the adaptive FIR filter
20 is used, the amount of computation required to generate the
reference signals r (r0, r1, . . . , rM-1) can be significantly
reduced.
Since the gain G(f) can be compensated for using the correction
coefficients h0, h1, . . . hM-1 of the FIR filter 20, as
illustrated in FIG. 11, in the active vibratory noise control
apparatus 10C according to the fourth embodiment of the present
invention, a reference signal generator 22C of an active vibratory
noise control device 12C can be configured such that the gain
setter 64 is removed and can be configured using the correction
data storage device 52A (the data of the gain G in the data stored
in the correction data storage device 52A, as illustrated in FIG.
10, is not used), the address corrector 62, and the waveform data
storage device 30.
Furthermore, also in the active vibratory noise control apparatuses
10B and 10C in the examples illustrated in FIGS. 9 and 11, for
example, as schematically illustrated in FIG. 12, in the active
vibratory noise control apparatus 10D according to the fifth
embodiment of the present invention, which corresponds to the
active vibratory noise control apparatus 10A in the example
illustrated in FIG. 8, which targets a plurality of orders, in
addition to vibratory noise NS called rotational second-order
component having a frequency that is twice as high as the engine
rotational speed Ne, that is, having the control frequency f
described above, vibratory-noise canceling sound can be used for
vibratory noise NS of the fourth-order component, sixth-order
component, and the like at the position of the microphone 8.
Even in this case, the frequency components of the order p to be
controlled are represented by f1=f.times.p1=f.times.1 (second-order
component), f2=f.times.p2=f.times.2 (fourth-order component), and
f3=f.times.p3=f.times.3 (sixth-order component).
A frequency detector 16A outputs, in addition to the detected
control frequency f=f1, the control frequencies f2 and f3 obtained
y multiplying the control frequency f by two and three,
respectively.
Then, in an address setter 60A in a basic signal generator 18C,
basic signals represented by Expression (11) below can be generated
by reading waveform data at the addresses i1, i2, and i3 for each
corresponding sampling pulse from the waveform data storage device
30: cos 2.pi.f1t, cos 2.pi.f2t, cos 2.pi.f3t (11)
An adder 33 generates a basic signal cos=cos 2.pi.f1t+cos
2.pi.f2t+cos 2.pi.f3t, and inputs the basic signal cos to an
adaptive FIR filter 20.
A correction data storage device 52B configured to generate a
reference signal r stores corrected address values ic1, ic2, and
ic3 of each phase delay .phi. corresponding to the control
frequencies f (f=f1, f2, f3), and supplies the corrected address
values ic1, ic2, and ic3 to an address corrector 62A as address
shift values.
A reference signal generator 22D generates a reference signal r
represented by Equation (12) below by reading waveform data at
addresses i1+ic1, i2+ic2, and i3+ic3 that are shifted by the
corrected address values ic1, ic2, and ic3 from the address
corrector 62A, respectively, and adding the results using an adder
59: r=cos {2.pi.f1t+.phi.(f1)}+cos {2.pi.f2t+.phi.f2)}+cos
{2.pi.f3t+.phi.f3)} (12)
Then, the reference signal r represented by Equation (12)
corresponding to the number of taps M of the adaptive FIR filter 20
is stored in a FIFO manner as a reference signal r0, r1, . . . , rM
for each delay time T in each storage area of a buffer 24 having M
storage areas (memory addresses).
Subsequently, a filter coefficient updating device 26 calculates
the individual filter coefficients h0, h1, . . . , hM-1 of the
adaptive FIR filter 20 in a manner similar to that described
above.
In the active vibratory noise control apparatus 10D according to
the fifth embodiment of the present invention, since the adaptive
FIR filter 20 is used as an adaptive filter that generates a
control signal Sc, reference signals r corresponding to components
of a plurality of orders are generated by reading waveform data at
address values i1+ic1, i2+ic2, and i3+ic3 that are shifted by
correction values (corrected address values or address shift
values) ic1, ic2, and ic3 of the address corresponding to a
correction value (here, the phase delay .phi.) in the transfer
characteristics in the passenger compartment space of the control
frequency f with respect to the addresses 11, i2, and i3 at which
basic cosine wave signals cos 2.pi.f1t, cos 2.pi.f2t, and cos
2.pi.f3t are generated. Thus, the computational load required to
generate the reference signals r can be significantly reduced.
Even in this case, like the third embodiment illustrated in FIG. 9,
as illustrated in FIG. 13, in the active vibratory noise control
apparatus 10E according to the sixth embodiment of the present
invention, a correction data storage device 52C may store gains
G(f1), G(f2), and G(f3) corresponding to control frequencies f1,
f2, and f3, respectively, and a reference signal generator 22E may
be configured such that the gains G(f1), G(f2), and G(f3) can be
set in gain setters 64A, 64B, and 64C, respectively. In this
manner, the gains G(f1), G(f2), and G(f3) can be individually set
in the reference signal generator 22E, thus allowing the filter
coefficient updating device 26 of the order component of the
corresponding control frequency f (f1, f2, or f3) to reduce the
convergence time.
In the active vibratory noise control apparatus according to the
embodiments of the present invention, the computational load
required to generate a reference signal can be reduced even when an
adaptive FIR filter instead of an adaptive notch filter as
disclosed in Japanese Patent No. 3843082 or No. 4074612 is used as
an adaptive filter that generates a control signal.
In the active vibratory noise control apparatus according to the
embodiments of the present invention, when vibratory noise of
components of a plurality of orders is to be canceled (or to be
controlled), an adaptive FIR filter in which a smaller increase in
the computational load required to generate a reference signal than
that with the use of an adaptive notch filter can be achieved.
A description will now be given together with reference numerals
illustrated in the accompanying drawings for ease of understanding.
Thus, it is to be understood that the elements described
hereinbelow are not to be construed as being limited to those with
the numerals.
For example, as illustrated in FIGS. 1 and 2, in an embodiment of
the present invention, an active vibratory noise control apparatus
(10) includes a basic signal generating means (18) that generates a
basic sine wave signal (sin) and a basic cosine wave signal (cos),
each of the basic sine wave signal (sin) and the basic cosine wave
signal (cos) having a frequency (f) that is based on a frequency of
vibratory noise generated from a vibratory noise source (2), and
outputting the basic sine wave signal (sin) and the basic cosine
wave signal (cos) as basic signals; an adaptive finite impulse
response filter (20) that outputs a control signal (Sc) based on
the basic cosine wave signal (cos) or the basic sine wave signal
(sin) in order to cancel the vibratory noise (NS) generated from
the vibratory noise source (2); a vibratory noise canceller (6)
that generates vibratory-noise canceling sound (SS) based on the
control signal (Sc); an error signal detector (8) that outputs an
error signal (e) that is based on a difference between the
vibratory noise (NS) and the vibratory-noise canceling sound (SS);
a reference signal generator (22) that generates a reference signal
(r) by correcting the basic cosine wave signal (cos) and the basic
sine wave signal (sin) based on correction values (also see FIGS. 5
and 6) regarding transfer characteristics from the vibratory noise
canceller (6) to the error signal detector (8), which correspond to
the frequencies (f) of the basic signals, and determining a sum of
the corrected basic cosine wave signal (C(f).times.cos) and the
corrected basic sine wave signal (D(f).times.sin), and that outputs
the sum as the reference signal (r); a buffer (24) that accumulates
a number (M) of reference signals (r0, r1, . . . , rM-1)
corresponding to the number of taps (M) of the adaptive finite
impulse response filter (20); and a filter coefficient updater (26)
that sequentially updates filter coefficients (h0, h1, . . . ,
hM-1) of the adaptive finite impulse response filter (20) so that
the error signal (e) can be minimized based on the error signal (e)
and the reference signals (r0, r1, . . . , rM-1) accumulated in the
buffer (24).
According to the embodiment of the present invention, in an active
vibratory noise control apparatus including an adaptive FIR filter,
a reference signal generator generates a reference signal by
correcting a basic signal using a correction value regarding
transfer characteristics corresponding to the frequency of a basic
signal having a frequency that is based on the frequency of
vibratory noise, and a buffer accumulates in sequence a number of
reference signals corresponding to the number of taps of the
adaptive FIR filter. A filter coefficient updating device updates
filter coefficients of the adaptive FIR filter using the reference
signal and an error signal that is based on the difference between
the vibratory noise and a vibratory-noise canceling sound so that
the error signal can be minimized. Since an adaptive FIR filter is
used, the amount of computation required to generate a reference
signal can be significantly reduced.
Further, for example, as illustrated in FIGS. 1 and 11, in another
embodiment of the present invention, an active vibratory noise
control apparatus (10C) includes a basic signal generating means
(18B) including a waveform data storage device (30: also see FIG.
3) that stores, as waveform data, when outputting a basic signal
(cos 2.pi.ft) having a frequency (f) that is based on a frequency
of vibratory noise generated from a vibratory noise source (2),
instantaneous value data obtained at segment positions determined
by dividing a sine wave or cosine wave of one period by a
predetermined number, the basic signal generating means (18B)
reading waveform data from the waveform data storage device (30)
for each sampling and generating the basic signal (cos 2.pi.ft); an
adaptive finite impulse response filter (20) that outputs a control
signal (Sc) based on the basic signal (cos 2.pi.ft) in order to
cancel the vibratory noise (NS) generated from the vibratory noise
source (2); a vibratory noise canceller (6) that generates
vibratory-noise canceling sound (SS) based on the control signal
(Sc); an error signal detector (8) that outputs an error signal (e)
that is based on a difference between the vibratory noise (NS) and
the vibratory-noise canceling sound (SS); a reference signal
generator (22C) including a correction data storage device (52A)
that stores, when correcting the basic signal (cos 2.pi.ft) based
on a correction value (also see FIGS. 5 and 6) regarding transfer
characteristics from the vibratory noise canceller (6) to the error
signal detector (8), which corresponds to the frequency (f) of the
basic signal (cos 2.pi.ft), and when outputting the corrected basic
signal as a reference signal (r), the correction value with respect
to the frequency (f) of the basic signal (cos 2.pi.ft), the
reference signal generator (22C) generating the reference signal
(r) by referring to the frequency (f) of the basic signal (cos
2.pi.ft), reading the correction value (ic) from the correction
data storage device (52A), and reading the waveform data from a
position that is shifted by the correction value (ic) with respect
to an address (i) at which the basic signal generating means (18B)
reads the waveform data from the waveform data storage device (30);
a buffer (24) that accumulates a number (M) of reference signals
(r0, r1, . . . , rM-1) corresponding to the number of taps (M) of
the adaptive finite impulse response filter (20); and a filter
coefficient updater (26) that sequentially updates filter
coefficients (h0, h1, . . . , hM-1) of the adaptive finite impulse
response filter (20) so that the error signal (e) can be minimized
based on the error signal (e) and the reference signals (r0, r1, .
. . , rM-1) accumulated in the buffer (24).
According to the embodiment of the present invention, in an active
vibratory noise control apparatus including an adaptive FIR filter,
a reference signal generator includes a correction data storage
device that stores, when correcting a basic signal having a
frequency that is based on the frequency of vibratory noise based
on a correction value regarding transfer characteristics, which
corresponds to the frequency of the basic signal, and when
outputting the corrected basic signal as a reference signal, the
correction value with respect to the frequency of the basic signal.
The reference signal generator generates a number of reference
signals corresponding to the number of taps of the adaptive FIR
filter by referring to the frequency of the basic signal, reading
the correction value from the correction data storage device, and
reading waveform data from a position that is shifted by the
correction value with respect to an address at which the waveform
data is read from a waveform data storage device, and accumulates
the reference signals in a buffer. Further, the reference signals
the number of which corresponds to the number of taps of the
adaptive FIR filter are used for updating and computation of filter
coefficients of the adaptive FIR filter. Since an adaptive FIR
filter is used, the amount of computation required to generate
reference signals can be significantly reduced.
Further, for example, as illustrated in FIG. 12, a basic signal
generating means (18C) outputs basic signals (cos=cos 2.pi.f1t+cos
2.pi.f2t+cos 2.pi.f3t) having frequencies of a plurality of orders
that are based on the frequency of the vibratory noise, and a
reference signal generator (22D) outputs reference signals [cos
{2.pi.f1t+.phi.(f1)}, cos {2.pi.f2t+.phi.(f2)}, cos
{2.pi.f3t+.phi.(f3)}] corresponding to the basic signals having the
frequencies of the plurality of orders.
Accordingly, the amount of computation for generating reference
signals can be reduced even when components of a plurality of
orders are to be controlled. In contrast, when an adaptive notch
filter is used, reference signal generators are provided in
parallel, resulting in a proportional increase in the amount of
computation in accordance with an increase in the number of
orders.
According to the embodiments of the present invention, therefore,
since an adaptive FIR filter is used as an adaptive filter that
generates a control signal, the computational load required to
generate a reference signal can be reduced.
According to the embodiments of the present invention, furthermore,
even when vibratory noise of components of a plurality of orders is
to be canceled (or to be controlled), since an adaptive FIR filter
is used as an adaptive filter that generates a control signal, a
small increase in the computational load required to generate a
reference signal can be achieved.
It is to be understood that the present invention is not to be
limited to the embodiments described above, and a variety of
modified configurations can be used.
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